CN114269974A

CN114269974A - Sheath-core filaments comprising crosslinkable and crosslinked binder compositions and methods of printing

Info

Publication number: CN114269974A
Application number: CN202080057965.8A
Authority: CN
Inventors: 罗斯·E·贝林; 托马斯·Q·查斯特克; 马克·E·纳皮耶腊拉; 亚历山大·J·库格尔; 肖恩·M·韦斯特; 罗伯特·D·韦德; 雅各布·D·扬
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2019-08-19
Filing date: 2020-08-12
Publication date: 2022-04-01
Also published as: EP4018024A1; US11725308B2; US20220290335A1; WO2021033084A1

Abstract

The present invention provides a sheath-core filament comprising a crosslinkable binder core curable with ultraviolet or visible radiation. These cross-linkable adhesive core compositions can provide very high bond strength and can replace traditional mechanical fasteners in many industrial applications. Sheath-core filaments comprising such crosslinkable compositions, crosslinked compositions, articles containing these compositions, and methods of making articles are provided. The crosslinkable composition contains a pendant aromatic ketone group or a pendant (meth) acryloyl group that results in the formation of crosslinks within the polymeric material upon exposure to ultraviolet radiation. The crosslinked composition is useful as a pressure sensitive adhesive.

Description

Sheath-core filaments comprising crosslinkable and crosslinked binder compositions and methods of printing

Technical Field

The present disclosure broadly relates to sheath-core filaments comprising a crosslinkable adhesive core and a non-tacky sheath, articles containing these compositions, and methods of making the articles.

Background

It has long been known to use melt filament fabrication (FFF) to produce three-dimensional articles, and these processes are generally referred to as methods of so-called 3D printing (or additive manufacturing). In FFF, plastic filaments are melted in a moving print head to form a printed article in a layer-by-layer, additive manner. The filaments are typically composed of polylactic acid, nylon, polyethylene terephthalate (typically glycol-modified) or acrylonitrile butadiene styrene.

(meth) acrylate-based pressure sensitive adhesives have been used in a variety of applications.

Disclosure of Invention

Provided herein are sheath-core filaments comprising a crosslinkable adhesive composition in the core, the crosslinkable adhesive composition being curable using ultraviolet or visible radiation. The crosslinkable binder composition has desirable flow characteristics for various applications. Sheath-core filaments comprising such crosslinkable compositions, crosslinked compositions, articles containing these compositions, and methods of making articles are provided. The crosslinkable composition contains a pendant aromatic ketone group or a pendant (meth) acryloyl group that results in the formation of crosslinks within the polymeric material upon exposure to ultraviolet radiation. The crosslinked composition is useful as a pressure sensitive adhesive.

In a first aspect, there is provided a sheath-core filament, comprising:

a non-tacky skin, wherein the non-tacky skin exhibits a melt flow index of less than 15 grams per 10 minutes (g/10 min); and

a curable adhesive composition comprising (1) a curable (meth) acrylate copolymer having a weight average molecular weight in the range of 100,000Da to 1,500,000Da and (2) optionally a photoinitiator, wherein the curable (meth) acrylate copolymer comprises:

a) a first monomer unit of formula (I) in an amount ranging from 50 to 99 weight percent based on the total weight of monomer units in the curable (meth) acrylate copolymer

Wherein

R₁Is hydrogen or methyl; and is

R₂Is an alkyl, heteroalkyl, aryl, aralkyl or alkaryl group;

b) a second monomer unit of formula (II) in an amount ranging from 1 to 13 weight percent based on the total weight of monomer units in the curable (meth) acrylate copolymer

Wherein

R₁Is hydrogen or methyl; and is

R₄is-OH, -NH₂A secondary amino group, a tertiary amino group, an (N, N-dialkylaminoalkyl) -O-group, an (N, N-dialkylaminoalkyl) -N-group; and

c) a third monomer unit of formula (III) in an amount ranging from 0.05 to 5 weight percent based on the total weight of monomer units of the curable (meth) acrylate copolymer

Wherein

R₃Comprising 1) an aromatic ketone group which causes hydrogen abstraction from the polymer chain when subjected to ultraviolet radiation or 2) a (meth) acryloyl group which undergoes free radical polymerization in the presence of a photoinitiator when subjected to ultraviolet or visible radiation.

In another aspect, a cured adhesive composition comprising the disclosed sheath-core filaments is provided, the cured adhesive composition being a reaction product resulting from subjecting the sheath-core filaments to ultraviolet or visible radiation after compounding the sheath-core filaments through a heated extruder nozzle.

In another aspect, there is provided a method of making a sheath-core filament, the method comprising:

a) forming a core composition comprising the disclosed curable binder composition;

b) forming a skin composition comprising a non-tacky thermoplastic material; and

c) wrapping the sheath composition around the core composition to obtain the sheath-core filament, wherein the sheath-core filament has an average longest cross-sectional distance in a range of 1mm to 20 mm.

The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The following description more particularly exemplifies illustrative embodiments. In several places throughout this application, guidance is provided through lists of examples, which examples can be used in various combinations. In each case, the lists cited are intended as representative groups only and are not to be construed as exclusive lists.

Drawings

Fig. 1 is a schematic exploded perspective view of a segment of a sheath-core filament according to an embodiment of the present disclosure.

Fig. 2 is a schematic cross-sectional view of a sheath-core filament according to an embodiment of the present disclosure.

Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the scope and spirit of the principles of this disclosure. The figures may not be drawn to scale.

Detailed Description

A sheath-core filament is provided that includes a crosslinkable adhesive core that is curable using ultraviolet or visible radiation. These cross-linkable adhesive core compositions can provide very high bond strength and can replace traditional mechanical fasteners in many industrial applications. Manufacturers also appreciate these bonding solutions because they are economical and easy to use. Sheath-core filaments comprising such crosslinkable compositions, crosslinked compositions, articles containing these compositions, and methods of making articles are provided. The crosslinkable composition contains a pendant aromatic ketone group or a pendant (meth) acryloyl group that results in the formation of crosslinks within the polymeric material upon exposure to ultraviolet radiation. The crosslinked composition is useful as a pressure sensitive adhesive.

Adhesive transfer tapes have been widely used to adhere a first substrate to a second substrate. Adhesive transfer tapes are typically provided in rolls and contain a pressure sensitive adhesive layer on a release liner or between two release liners, and because the transfer adhesive tape typically needs to be die cut to the desired size and shape prior to application to a substrate, the transfer adhesive tape outside the die cut area is discarded as waste. The sheath-core filaments described herein can be used to deliver pressure sensitive adhesives (also referred to herein as "hot melt processable adhesives") without the use of a release liner and with less waste. The non-tacky skin allows for easy handling of the hot melt processable adhesive prior to deposition on a substrate. In addition, the use of sheath-core filaments as the adhesive composition described herein can greatly reduce the waste typically associated with adhesive transfer tapes because die cutting is not required because the adhesive is only deposited in the desired areas.

The disclosed sheath-core filaments can be used to print hot melt processable adhesives using melt filament fabrication ("FFF"). The material properties required for FFF dispensing are generally significantly different from those required for hot melt dispensing of pressure sensitive adhesive compositions. For example, in the case of conventional hot melt adhesive dispensing, the adhesive is melted into a liquid in a tank and pumped out through a hose and nozzle. Thus, conventional hot melt adhesive dispensing requires a low melt viscosity adhesive, which is typically quantified as a high Melt Flow Index (MFI) adhesive. If the viscosity is too high (or the MFI is too low), the hot melt adhesive cannot be effectively transferred from the tank to the nozzle. In contrast, FFF involves melting the filaments only within the nozzle at the time of dispensing and is therefore not limited to a low melt viscosity adhesive (high melt flow index adhesive) that can be easily pumped. Indeed, a high melt viscosity adhesive (low melt flow index adhesive) may advantageously provide geometric stability of the hot melt processable adhesive after dispensing, which allows for precise and controlled placement of the adhesive, as the adhesive does not excessively spread after printing.

Furthermore, filaments suitable for FFF typically require at least a certain minimum tensile strength so that large spools of filaments can be fed continuously to the nozzle without breaking. FFF filaments are typically wound into horizontally wound rolls. When the filaments are wound into a horizontally wound roll, the material closest to the center may be subjected to high compressive forces. Preferably, the sheath-core filaments are resistant to permanent cross-sectional deformation (i.e., compression set) and self-adhesion (i.e., blocking during storage).

The disclosed sheath-core filaments comprising the crosslinkable composition are particularly well suited for application to rough surfaces and/or for adhesion to high surface energy surfaces. Desirably, the crosslinked composition can be cleanly removed from a variety of surfaces, if desired. In addition, these crosslinkable compositions can be formulated to be transparent and useful in a variety of applications where this property is beneficial.

In many embodiments, the disclosed sheath-core filaments are pressure sensitive adhesive compositions upon dispensing. According to the Pressure-Sensitive Tape Council (Pressure-Sensitive Tape Council), a Pressure-Sensitive adhesive (PSA) is defined as having the following properties: (1) strong and permanent tack, (2) bondable by light finger pressure, (3) sufficient ability to remain on the adherend, and (4) sufficient cohesive strength to be cleanly removed from the adherend. Materials that have been found to function adequately as PSAs include polymers designed and formulated to exhibit the desired viscoelastic properties that achieve the desired balance of initial tack, peel adhesion, and shear holding power. PSAs are characterized as generally tacky at room temperature. Materials that are only tacky or adhere to a surface do not constitute a PSA; the term PSA encompasses materials with additional viscoelastic properties. PSAs are adhesives that meet the Dahlquist criteria for tack, meaning that the shear storage modulus is typically 3X 10 when measured at 25 ℃ and 1 Hz (6.28 rad/sec)⁵Pa (300kPa) or less. PSAs typically exhibit adhesion, cohesion, compliance, and elasticity at room temperature.

The term "adhesive composition" may refer herein to an adhesive containing a curable (meth) acrylate copolymer and/or a cured (meth) acrylate copolymer. In many embodiments, the adhesive composition is a pressure sensitive adhesive composition.

As used herein, the terms "a," "an," and "the" are not intended to refer to only a single entity, but include the general class of which a particular example may be used for illustration. These terms may be used interchangeably with the term "at least one".

As used herein, the term "room temperature" refers to a temperature of from about 20 ℃ to about 25 ℃, or from about 22 ℃ to about 25 ℃.

The term "and/or" means one or all of the listed elements or a combination of any two or more of the listed elements.

The phrase "in the range of … …" or similar phrases refers to all values within the stated range plus the endpoints of that range.

The term "(meth) acryloyl" refers to the formula H₂C＝CR₁A radical of formula (II) (CO) -, wherein R₁Is hydrogen or methyl. That is, the (meth) acryloyl group is an acryloyl group (wherein R is₁Is hydrogen) and/or a methacryloyl group (wherein R is₁Is methyl). The (meth) acryloyl group is typically of the formula H₂C＝CR₁(meth) acryloyloxy radical of- (CO) -O-, or of the formula H₂C＝CR₁(meth) acrylamido groups of- (CO) -NH-.

The term "(meth) acrylate copolymer" refers to a polymeric material formed from two or more monomers (e.g., three or more monomers), wherein a majority (at least 50, at least 60, at least 70, at least 80, or at least 90 weight%) of the monomers used to form the copolymer are (meth) acrylates (e.g., alkyl (meth) acrylates, aryl (meth) acrylates, aralkyl (meth) acrylates, alkaryl (meth) acrylates, and heteroalkyl (meth) acrylates). The term (meth) acrylate includes methacrylates, acrylates, or both. The term (meth) acrylate copolymer may be applicable herein to the precursor (meth) acrylate copolymer, and/or the curable (meth) acrylate copolymer, and/or the cured (meth) acrylate copolymer.

As used herein, the term "precursor (meth) acrylate copolymer" refers to a (meth) acrylate copolymer that is free of third monomer units of formula (III) but can react with an unsaturated reagent compound to form a curable (meth) acrylate copolymer. That is, the precursor (meth) acrylate copolymer may be converted to a curable (meth) acrylate copolymer having pendant formula (meth) acryloyl groups that are the second type of third monomer units of formula (III).

As used herein, the term "curable (meth) acrylate copolymer" refers to a (meth) acrylate copolymer having a third monomer unit of formula (III) in addition to the first monomer unit of formula (I) and the second monomer unit of formula (II). The third monomer unit of formula (III) can be of the first type (having an aromatic ketone group), the second type (having a pendant formula (meth) acryloyl group), or both. The third monomer unit may react upon exposure to ultraviolet radiation (or ultraviolet or visible radiation in the presence of a photoinitiator). When the third monomer unit reacts to form a cured (meth) acrylate copolymer, covalent bonds are formed between different polymer chains or within the same polymer chain. This reaction generally increases the weight average molecular weight of the (meth) acrylate copolymer.

As used herein, the term "cured (meth) acrylate copolymer" refers to a (meth) acrylate copolymer resulting from exposure of a curable (meth) acrylate copolymer to ultraviolet radiation (or to ultraviolet or visible radiation in the presence of a photoinitiator). In some embodiments, a material is considered cured when at least 50% (e.g., at least 60%, at least 70%, at least 80%, at least 90%, or at least 95%) by weight of the groups of formula (III) have reacted to form crosslinking sites.

Sheath-core filament

Fig. 1 schematically shows an example of a sheath-core filament 20. The filament includes a core 22 and a sheath 24 that surrounds (encapsulates) an outer surface 26 of the core 22. Fig. 2 shows a sheath-core filament 30 in cross-section. The core 32 is surrounded by a sheath 34. Any desired cross-sectional shape may be used for the core. For example, the cross-sectional shape may be circular, oval, square, rectangular, triangular, and the like. The cross-sectional area of core 32 is generally greater than the cross-sectional area of sheath 34. In addition to shape and area, the cross-section of the filament also includes cross-sectional distance. The cross-sectional distance is equal to the length of the chord that can engage a point on the perimeter of the cross-section. The term "longest cross-sectional distance" refers to the maximum length of a chord that can be drawn across a cross-section of a filament at a given position along its axis.

Sheath-core filaments typically have a relatively narrow longest cross-sectional distance (e.g., the diameter of a core having a circular cross-sectional shape) such that they can be used in applications where precise deposition of adhesive is desired or advantageous. For example, sheath-core filaments typically have an average longest cross-sectional distance in the range of 1 millimeter to 20 millimeters (mm). The average longest cross-sectional distance of the filaments may be at least 1mm, at least 2mm, at least 3mm, at least 4mm, at least 5mm, at least 6mm, at least 8mm, or at least 10mm, and may be at most 20mm, at most 18mm, at most 15mm, at most 12mm, at most 10mm, at most 8mm, at most 6mm, or at most 5 mm. The average length may be in the range of, for example, 2mm to 20mm, 5mm to 15mm, or 8mm to 12 mm.

Typically, 1% to 10% of the longest cross-sectional distance (e.g., diameter) of the sheath-core filament is the sheath, and 90% to 99% of the longest cross-sectional distance (e.g., diameter) of the sheath-core filament is the core. For example, at most 10%, at most 8%, at most 6%, or at most 4% and at least 1%, at least 2%, or at least 3% of the longest cross-sectional distance may be due to the sheath, with the remainder being due to the core. The sheath extends completely around the core to prevent the core from sticking to itself. However, in some embodiments, the ends of the filaments may contain only the core.

Typically, the sheath-core filaments have an aspect ratio of length to longest cross-sectional distance (e.g., diameter) of 50:1 or greater, 100:1 or greater, or 250:1 or greater. Sheath-core filaments having a length of at least about 20 feet (6 meters) can be used to print hot melt processable adhesives. Depending on the application or use of the sheath-core filament, it may be desirable to have a relatively uniform longest cross-sectional distance (e.g., diameter) over its length. For example, an operator may calculate the amount of material being melted and dispensed based on the expected filament mass per predetermined length; but if the mass per unit length varies greatly, the amount of material dispensed may not match the calculated amount. In some embodiments, the sheath-core filament has a maximum variation in the longest cross-sectional distance (e.g., diameter) of 20% over a length of 50 centimeters (cm), or even a maximum variation in the longest cross-sectional distance (e.g., diameter) of 15% over a length of 50 cm.

The sheath-core filaments described herein can exhibit a variety of desirable properties both as prepared and as hot melt processable adhesive compositions. When formed, the sheath-core filaments desirably have a strength consistent with not fracturing or tearing the sheath upon disposal. The structural integrity required of the sheath-core filament varies depending on the particular application in which it is used. Preferably, the sheath-core filament has a strength that conforms to the requirements and parameters of one or more additive manufacturing devices (e.g., 3D printing systems). However, when feeding the filaments to the deposition nozzle, one additive manufacturing apparatus may subject the sheath-core filaments to a greater force than a different apparatus.

Advantageously, the sheath material of the sheath-core filaments typically has an elongation at break of 50% or greater, 60% or greater, 80% or greater, 100% or greater, 250% or greater, 400% or greater, 750% or greater, 1000% or greater, 1400% or greater, or 1750% or greater and 2000% or less, 1500% or less, 900% or less, 500% or less, or 200% or less. In other words, the elongation at break of the sheath material of the sheath-core filament may be in the range of 50% to 2000%, 50% to 1000%, or 60% to 1000%. In some embodiments, the elongation at break is at least 60%, at least 80%, or at least 100%. Elongation at break can be measured, for example, by the method outlined in ASTM D638-14, using test specimen type IV.

Once the sheath-core filaments are melted and mixed, advantages provided by at least certain embodiments employing the sheath-core filaments as a pressure sensitive adhesive include one or more of the following: low Volatile Organic Compound (VOC) characteristics, avoidance of die cutting, design flexibility, implementation of complex non-planar bond patterns, printing on thin and/or fine substrates, and printing on irregular and/or complex topographical features.

The sheath-core filaments may be prepared using any suitable method known to those skilled in the relevant art. Most methods include forming the core composition as a hot melt processable adhesive. The hot melt processable adhesive in the core may be prepared as described below. The methods also include forming a sheath composition comprising a non-tacky thermoplastic material. These methods may further comprise wrapping the skin composition around the core composition.

In many embodiments, the method of making a sheath-core filament comprises co-extruding the core composition and the sheath composition through a coaxial die such that the sheath composition surrounds the core composition. The optional additives for the core composition, which is a hot melt processable adhesive, may be added to an extruder (e.g., a twin screw extruder) equipped with a side stuffer that allows for the inclusion of the additives. Similarly, optional additives may be added to the skin composition in the extruder. A hot melt processable adhesive core may be extruded through a central portion of the coaxial die having the appropriate longest cross-sectional distance (i.e., diameter), while a non-tacky skin may be extruded through an outer portion of the coaxial die. One suitable die is a filament spinning die as described in U.S. patent 7,773,834(Ouderkirk et al). Optionally, the filaments may be cooled using a water bath during extrusion. The filaments can be lengthened using a belt tractor. The speed of the belt tractor may be adjusted to achieve a desired filament cross-sectional distance (e.g., diameter).

In other embodiments, the core may be formed by extrusion of the core composition. The resulting core may be rolled within a sheath composition having dimensions sufficient to surround the core. In other embodiments, the core composition may be formed into a sheet. A stack of sheets having a thickness suitable for the filaments may be formed. The skin composition may be positioned around the stack such that the skin composition surrounds the stack.

Suitable components of the sheath-core filaments are described in detail below.

Leather

The sheath provides structural integrity to the sheath-core filament, as well as separating the adhesive core so that it does not adhere to itself (e.g., when the filament is provided in a roll or reel) or so that it does not prematurely adhere to another surface. The sheath is typically selected to be thick enough to support the filament form factor and allow delivery of the sheath-core filaments to the deposition site. On the other hand, the thickness of the sheath is selected such that its presence does not adversely affect the overall bonding properties of the sheath-core filament.

The sheath material is typically selected to have a melt flow index ("MFI") of less than or equal to 15 grams/10 minutes when measured at 190 ℃ and under a load of 2.16 kilograms according to ASTM D1238. Such low melt flow index indicates a sheath material that has sufficient strength (robustness) to allow the sheath-core filament to withstand the physical manipulations required for disposal, such as use with additive manufacturing equipment. During such processes, the sheath-core filament typically needs to be unwound from a reel, introduced into an additive manufacturing apparatus, and then advanced into a nozzle for melting and blending without breaking. A sheath material having a melt flow index of less than or equal to 15 grams/10 minutes is less prone to breaking (tensile stress failure) and may be wound into a spool or roll having a relatively small radius of curvature as compared to sheath materials having higher melt flow indices. In certain embodiments, the sheath material exhibits a melt flow index of 14 grams/10 minutes or less, 13 grams/10 minutes or less, 12 grams/10 minutes or less, 11 grams/10 minutes or less, 10 grams/10 minutes or less, 9 grams/10 minutes or less, 8 grams/10 minutes or less, 7 grams/10 minutes or less, 6 grams/10 minutes or less, 5 grams/10 minutes or less, 4 grams/10 minutes or less, 3 grams/10 minutes or less, 2 grams/10 minutes or less, or 1 gram/10 minutes or less. If desired, the various sheath materials can be blended (e.g., melted and blended) together to provide a sheath composition having a desired melt flow index.

Low melt flow index values tend to correlate with high melt viscosity and high molecular weight. Higher molecular weight sheath materials tend to result in better mechanical properties. That is, the skin material tends to be stronger (i.e., the skin material is tougher and is less likely to undergo tensile stress cracking). This increased robustness is generally a result of an increased level of polymer chain entanglement. For other reasons, higher molecular weight sheath materials are often advantageous. For example, these skin materials tend to migrate less to the adhesive/substrate interface in the final article; such migration may adversely affect adhesion performance, especially under aging conditions. However, in some cases, block copolymers having relatively low molecular weights behave like high molecular weight materials due to physical crosslinking. That is, despite the relatively low molecular weight of the block copolymers, they may still have low MFI values and good toughness.

As the melt flow index decreases (such as to less than or equal to 15 grams/10 minutes), less sheath material is required to achieve the desired mechanical strength. That is, the thickness of the sheath layer may be reduced and its contribution to the overall longest cross-sectional distance (e.g., diameter) of the sheath-core filament may be reduced. This is advantageous because if the sheath material is present in an amount greater than about 10 weight percent of the total weight of the filaments, it can adversely affect the adhesive properties of the core pressure sensitive adhesive.

For application to a substrate, the sheath-core filaments are typically melted and mixed together prior to deposition onto the substrate. It is desirable to blend the sheath material with the hot melt processable adhesive in the core without adversely affecting the properties of the hot melt processable adhesive. In order to effectively blend the two compositions, it is generally desirable that the sheath composition be compatible with the core composition. The haze of the finally compounded core and sheath indicates the compatibility of the two materials, with the final adhesive having a low haze (e.g., less than 5%) being highly compatible, while the core and sheath compositions having a high haze (e.g., greater than 20% or especially greater than 50%) may be the result of phase separation between the core and sheath compositions.

If the sheath-core filament is formed by coextrusion of the core and sheath compositions, it is desirable to select the melt viscosity of the sheath composition to be quite similar to the melt viscosity of the core composition. If the melt viscosities are not sufficiently similar (e.g., if the melt viscosity of the core composition is significantly lower than the melt viscosity of the sheath composition), the sheath may not surround the core in the filament. The filament may then have an exposed core region, and the filament may be adhered to itself. In addition, if the melt viscosity of the sheath-core composition is significantly higher than the core composition, the non-tacky sheath may remain exposed (not fully blended with the core) and adversely affect the formation of an adhesive bond with the substrate during melt blending of the core and sheath compositions during dispensing. The ratio of the melt viscosity of the sheath composition to the melt viscosity of the core composition is in the range of 100:1 to 1:100, in the range of 50:1 to 1:50, in the range of 20:1 to 1:20, in the range of 10:1 to 1:10, or in the range of 5:1 to 1: 5. In many embodiments, the melt viscosity of the sheath composition is greater than the melt viscosity of the core composition. In this case, the ratio of the viscosity of the sheath composition to the core composition is typically in the range of 100:1 to 1:1, in the range of 50:1 to 1:1, in the range of 20:1 to 1:1, in the range of 10:1 to 1:1, or in the range of 5:1 to 1: 1.

In addition to exhibiting strength, the sheath material is non-tacky. A material is non-tacky if it passes a "self-tack test" in which the force required to peel the material from itself is equal to or less than a predetermined maximum threshold amount without fracturing the material. The use of a non-tacky skin allows the filament to be handled and optionally printed without undesirably adhering to anything prior to deposition onto a substrate.

In certain embodiments, the sheath material exhibits a combination of at least two of a low MFI (e.g., less than or equal to 15 grams/10 minutes) as determined by ASTM D1238-13, a moderate elongation at break (e.g., 100% or more as determined by ASTM D638-14 using test specimen type IV), a low tensile stress at break (e.g., 10MPa or more as determined by ASTM D638-14 using test specimen type IV), and a moderate shore D hardness (e.g., 30-70 as determined by ASTM D2240-15). Skins having at least two of these properties tend to have a toughness suitable for FFF-type applications.

In some embodiments, for the purpose of providing structural integrity and a non-tacky surface, the sheath comprises a material selected from the group consisting of styrene copolymers (e.g., styrene block copolymers such as styrene-butadiene block copolymers), polyolefins (e.g., polyethylene, polypropylene, and copolymers thereof), ethylene vinyl acetate, polyurethane, ethylene methyl acrylate copolymers, ethylene (meth) acrylic acid copolymers, nylon, (meth) acrylic acid block copolymers, poly (lactic acid), anhydride-modified ethylene acrylate resins, and the like. Depending on the process of making the sheath-core filament, it may be advantageous to match the polarity of the sheath polymer material at least slightly to the polarity of the polymer in the core. It may be advantageous to use a skin material that includes polar groups such as, for example, oxy groups, carbonyl groups, amino groups, amido groups, ether groups, ester groups, thiol ether groups, and combinations thereof.

Suitable styrenic materials for the skin are commercially available and include, for example and without limitation, those available under the tradenames KRATON (e.g., KRATON D116 851118, D1119, and a1535) from KRATON high Performance Polymers (Houston, TX, USA) under the tradename SOLPRENE S (e.g., SOLPRENE S-1205), dansheng (Houston, USA) under the tradename dynal (e.g., dynal S-1205), intarsia chemical (Louisville, kyi, USA), VECTOR and TAIPOL rubber limited (louisiana, New Orleans rc, USA) under the tradename flukulark, nilla, USA and tsen Corporation, resk, USA under the tradenames tsk-35k, such as benzene 76, ultraa) (Ineos stilation (Aurora, IL, USA)).

Suitable polyolefins are not particularly limited. Suitable polyolefin resins include, for example, but are not limited to, polypropylene (e.g., polypropylene homopolymer, polypropylene copolymer, and/or blends comprising polypropylene), polyethylene (e.g., polyethylene homopolymer, polyethylene copolymer, high density polyethylene ("HDPE"), medium density polyethylene ("MDPE"), low density polyethylene ("LDPE"), and combinations thereof.e., suitable commercially available LDPE resins include petrothrene NA217000 available from linad basell (Rotterdam, Netherlands) having an MFI of 5.6 grams/10 minutes, MARLEX 1122 available from snowdronlnpis corporation (german paddock, TX), suitable HDPE resins include Midland available from rodon Chemical Company (e.g., sandlo corp., USA) (Dow Company, Midland, USA) and exxon, fuson corp corporation (nmobil corporation, 5960, USA), TX, USA)) of HDPE HD 6706 series. Polyolefin block copolymers are available from the dow chemical company under the trade name INFUSE (e.g., INFUSE 9807).

Suitable commercially available thermoplastic polyurethanes may include, for example, but are not limited to, ESTANE 58213 and ESTANE ALR 87A available from Lubrizol Corporation (Wickliffe, OH) of Loborun, Ohio.

Suitable ethylene vinyl acetate ("EVA") polymers (i.e., copolymers of ethylene and vinyl acetate) for use in the skin include resins available from Dow, Midland, michigan under the trade name ELVAX. Typical vinyl acetate contents range from 9 to 40 weight percent grades and melt flow indices as low as 0.3 grams/10 minutes. One exemplary material is ELVAX 3135SB with an MFI of 0.4 g/10min (according to ASTM D1238). Suitable EVA's also include high vinyl acetate ethylene copolymers available under the tradename ultrethlene from liendbasell (Houston, TX). Typical vinyl acetate content is in the grade range of 12 wt% to 18 wt%. Suitable EVA's also include EVA copolymers available under the trade name ATEVA from Seranis Corporation (Celanese Corporation (Dallas, TX)). Typical vinyl acetate content is in the order of 2 to 26% by weight.

Suitable nylon materials for the sheath include nylon terpolymers available from nylon corporation of america under the trade name NYCOA CAY.

Suitable ethylene acrylate copolymers for the skin (e.g., ethylene-methyl acrylate copolymers) include resins available from dow corporation (midland, michigan) under the trade name ELVALOY (e.g., ELVALOY 1330 having 30% methyl acrylate and an MFI of 3.0 g/10min, ELVALOY 1224 having 24% methyl acrylate and an MFI of 2.0 g/10min, and ELVALOY 1609 having 9% methyl acrylate and an MFI of 6.0 g/10 min).

Suitable anhydride-modified ethylene acrylate resins are available from the dow company under the trade name BYNEL, such as BYNEL 21E533 with an MFI of 7.3 g/10min and BYNEL 30E753 with an MFI of 2.1 g/10 min.

Suitable ethylene (meth) acrylic acid copolymers for the sheath include resins available from dow under the tradename NUCREL (e.g., NUCREL 925 with an MFI of 25.0 grams/10 minutes and NUCREL 3990 with an MFI of 10.0 grams/10 minutes).

Suitable (meth) acrylic block copolymers for the skin include block copolymers available from clony, Tokyo kingdom, japan (Kuraray, Chiyoda-ku, Tokyo, JP), under the trade name KURARITY (e.g., KURARITY LA2250 and KURARITY LA 4285). KURARITY LA2250 with an MFI of 22.7 g/10min is an ABA block copolymer with poly (methyl methacrylate) as the A block and poly (n-butyl acrylate) as the B block. About 30% by weight of the polymer is poly (methyl methacrylate). KURAITY LA4285, MFI 1.8 g/10min, is an ABA block copolymer having poly (methyl methacrylate) as the A block and poly (n-butyl acrylate) as the B block. About 50% by weight of the polymer is poly (methyl methacrylate). Varying the amount of poly (methyl methacrylate) in the block copolymer varies its glass transition temperature and its toughness.

Suitable poly (lactic acid) s for the skin include those available from Natureworks LLC (Minnetonka, NM, USA) under the trade name INGEO (e.g., INGEO6202D fiber grade).

The sheath typically comprises from 1 wt% to 10 wt% of the total weight of the sheath-core filament. The amount can be at least 1 wt%, at least 2 wt%, at least 3 wt%, at least 4 wt%, at least 5 wt%, and at most 10 wt%, at most 9 wt%, at most 8 wt%, at most 7 wt%, at most 6 wt%, or at most 5 wt%.

Core

The core comprises a curable (meth) acrylate copolymer. The curable (meth) acrylate copolymer comprises at least three different types of monomer units: a first monomer unit of formula (I), a second monomer unit of formula (II), and a third monomer unit of formula (III). Other optional monomer units may also be included in the curable (meth) acrylate copolymer. Depending on the choice of the third monomer unit comprising the group responsible for curing the (meth) acrylate copolymer, the curable (meth) acrylate copolymer may be formed directly from a polymerizable composition containing the corresponding first, second, third and other optional monomers. In some embodiments, particularly for curable (meth) acrylate copolymers having pendant formula (meth) acryloyl groups, a precursor (meth) acrylate copolymer is initially prepared and then further reacted with an unsaturated reagent compound to form a third monomer unit having a pendant formula (meth) acryloyl group and the resulting curable (meth) acrylate copolymer.

In other words, some curable (meth) acrylate copolymers are formed from precursor (meth) acrylate copolymers, while other curable (meth) acrylate copolymers are formed directly from their constituent monomers. The precursor (meth) acrylate copolymer does not have a third monomer unit of formula (III), but has a group in the fourth monomer unit of formula (IV) that can further react to form a third monomer unit of the second type of formula (III) having a (meth) acryloyl group. The precursor (meth) acrylate comprises a first monomer unit of formula (I) and a second monomer unit of formula (II). The curable (meth) acrylate copolymer formed from the precursor (meth) acrylate copolymer has a third monomer unit of formula (III) with a pendant formula (meth) acryloyl group. The cured (meth) acrylate copolymer is formed by subjecting the curable (meth) acrylate copolymer to ultraviolet radiation or by subjecting the curable (meth) acrylate copolymer to ultraviolet or visible radiation in the presence of a photoinitiator.

The curable (meth) acrylate copolymer comprises the first monomer unit of formula (I) in an amount ranging from 50 to 99 weight percent based on the total weight of monomer units in the curable (meth) acrylate copolymer.

In the formula (I), R₁Is hydrogen or methyl, and R₂Is an alkyl, heteroalkyl, aryl, aralkyl or alkaryl group. In other words, the first monomer units are derived from alkyl (meth) acrylates, heteroalkyl (meth) acrylates, aryl (meth) acrylates, arylalkyl (meth) acrylates, alkylaryl (meth) acrylates, or mixtures thereof (i.e., the (meth) acrylate copolymers can have a plurality of monomers with different R' s₂The first monomeric unit of the group). Suitable alkyl radicals R₂The group typically has 1 to 32 carbon atoms, 1 to 24 carbon atoms, 1 to 18 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 10 carbon atoms, 1 to 8 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. The alkyl group can be linear, branched, cyclic, or combinations thereof. Suitable heteroalkyl radicals R₂The radicals usually having from 1 to 30 carbon atoms orMore and 1 to 20 carbon atoms or more, 1 to 20 carbon atoms and 1 to 10 heteroatoms, 1 to 16 carbon atoms and 1 to 8 heteroatoms, 1 to 12 carbon atoms and 1 to 6 heteroatoms, or 1 to 10 carbon atoms and 1 to 5 heteroatoms. The heteroatom is typically oxygen (an oxy group), but may be sulfur (-S-group) or nitrogen (-NH-group). Suitable aryl radicals R₂The groups are typically carbocyclic aromatic groups. The aryl group typically has 6 to 12 carbon atoms or 6 to 10 carbon atoms. In many embodiments, aryl is phenyl. Suitable aralkyl groups have the formula-R-Ar, wherein R is an alkylene group and Ar is an aryl group. Alkylene groups, which are divalent groups of alkanes, typically have 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms, and aryl groups typically have 6 to 12 carbon atoms, 6 to 10 carbon atoms, or 6 carbon atoms. In many embodiments, aryl is phenyl. Suitable alkaryl groups are of the formula-Ar-R, wherein Ar is an arylene group (i.e. a divalent group of a carbocyclic aromatic compound) and R is an alkyl group. The arylene group typically has 6 to 12 carbon atoms, 6 to 10 carbon atoms, or 6 carbon atoms. In many embodiments, the arylene group is phenylene. The alkyl group of the alkylaryl group is the same as described above for the alkyl group, but typically has 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms.

R in the formula (I)₂The group is typically an alkyl group. In other words, the first monomer unit is typically derived from (i.e., formed from) an alkyl (meth) acrylate. Exemplary alkyl (meth) acrylates generally include, but are not limited to, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isoamyl (meth) acrylate, 2-methylbutyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-methyl-2-pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-methylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-octyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (n-butyl (meth) acrylate, isobutyl (n-2-butyl (meth) acrylate, isobutyl, Isobornyl (meth) acrylate, (meth) acrylic acid propyl esterAdamantyl enoate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, 2-propylheptyl (meth) acrylate, isotridecyl (meth) acrylate, isostearyl (meth) acrylate, octadecyl (meth) acrylate, 2-octyldecyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, and heptadecyl (meth) acrylate. Some other exemplary branched alkyl (meth) acrylates are (meth) acrylates of Guerbet alcohols having 12 to 32 carbon atoms, as described in PCT patent application publication WO 2011/119363(Clapper et al). In some embodiments, an alkyl (meth) acrylate having an alkyl group with no more than 8 carbon atoms is selected. These alkyl (meth) acrylates generally have higher solubility parameters than those having alkyl groups with more than 8 carbon atoms. This can increase the compatibility of the monomer with the (meth) acrylic acid or (meth) acrylamide used to form the second monomer unit.

Radical R₂May be a heteroalkyl, aryl, aralkyl or alkaryl group. Examples of monomers having heteroalkyl groups include, but are not limited to, ethoxyethyl (meth) acrylate, polyethylene glycol (meth) acrylate, and polypropylene glycol (meth) acrylate. Examples of such monomers include, but are not limited to, 2-phenylethyl acrylate, 3-phenylethyl acrylate, and 2-diphenylethyl acrylate.

The first monomer unit is typically selected to control the final glass transition temperature ("Tg") and shear storage modulus ("G'") of the (meth) acrylate copolymer and the adhesive. In many embodiments, the alkyl (meth) acrylate is an alkyl acrylate. The use of alkyl acrylates rather than alkyl methacrylates typically results in (meth) acrylate copolymers having lower glass transition temperatures and lower shear storage moduli (G'). A lower glass transition temperature and lower shear storage modulus (G') of the (meth) acrylate copolymer may be required to provide a pressure sensitive adhesive composition. The final glass transition temperature (Tg) of the (meth) acrylate copolymer is typically equal to at least-50 ℃, at least-40 ℃, at least-30 ℃, at least-20 ℃, at least-15 ℃, at least-10 ℃, at least-5 ℃ or at least 0 ℃, and typically no greater than 40 ℃, no greater than 30 ℃, no greater than 20 ℃ or no greater than 10 ℃. When the Tg exceeds 20 ℃, the adhesive may require heat activation (i.e., upon heating to slightly above Tg, the material becomes tacky and adheres with only finger pressure). When cooled below Tg, these heat-activated adhesives are no longer tacky, but have sufficient ability to remain on an adherend and sufficient cohesive strength to be cleanly removed from the adherend.

The curable (meth) acrylate copolymer comprises at least 50 wt% of the first monomer units based on the total weight of the curable (meth) acrylate copolymer. If the amount of the first monomer unit is less than at least 50 wt%, the glass transition temperature of the (meth) acrylate copolymer may not be suitable for the pressure-sensitive adhesive. For example, the (meth) acrylate copolymer typically comprises at least 55 wt%, at least 60 wt%, at least 65 wt%, at least 70 wt%, or at least 75 wt% of the first monomer unit. The amount of the first monomer unit may be up to 99 wt%. If the amount of the first monomer unit is more than 99% by weight, the amounts of the second monomer unit and the third monomer unit may be insufficient in the curable (meth) acrylate copolymer. For example, the amount may be up to 95 wt%, up to 90 wt%, up to 85 wt%, or up to 80 wt%. In some embodiments, the amount of the first monomer unit ranges from 50 wt% to 99 wt%, from 60 wt% to 99 wt%, from 70 wt% to 99 wt%, from 80 wt% to 99 wt%, from 60 wt% to 95 wt%, from 70 wt% to 95 wt%, or from 80 wt% to 90 wt%. The amount is based on the total weight of the (meth) acrylate copolymer.

The curable (meth) acrylate copolymer further comprises a second monomer unit of formula (II) in an amount in the range of 1 to 13 weight percent based on the total weight of monomer units in the curable (meth) acrylate copolymer.

The radical R1 is hydrogen or methyl. Radical R₄is-OH,-NH₂Secondary amino groups, tertiary amino groups, (N, N-dialkylaminoalkyl) -O-groups, (N, N-dialkylaminoalkyl) -N-groups. In other words, when R is₄is-NH₂When the second monomeric unit is derived from (meth) acrylamide, it means acrylamide and/or methacrylamide, or when R is₄When it is-OH, the second monomer unit is derived from (meth) acrylic acid, which refers to acrylic acid and/or methacrylic acid.

The second monomer unit advantageously provides hydrogen bonding within the curable (meth) acrylate copolymer. Such hydrogen bonding tends to enhance the dimensional stability of the adhesive filaments prior to dispensing. In other words, dimensional stability may be provided even if covalent crosslinks have not been formed in the curable (meth) acrylate copolymer (i.e., covalent crosslinks are formed from the third monomeric unit of the curable (meth) acrylate when subjected to ultraviolet radiation or when subjected to ultraviolet or visible radiation in the presence of a photoinitiator). The second monomer unit may also enhance adhesion of the cured adhesive composition to a substrate and/or enhance cohesive strength of both the curable and cured adhesive compositions.

Exemplary second monomer units having an acidic group can be, for example, carboxylic acid monomers. Exemplary acidic monomers include, but are not limited to, (meth) acrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleic acid, oleic acid, beta-carboxyethyl acrylate, and the like. In many embodiments, the monomer is (meth) acrylic acid.

An exemplary second monomer unit having a primary amido group is (meth) acrylamide. Exemplary second monomer units having a secondary amide group include, but are not limited to, (meth) acryloylmorpholine and N-alkyl (meth) acrylamides, such as N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-tert-octyl (meth) acrylamide or N-octyl (meth) acrylamide. Exemplary second monomer units having a tertiary amide group include, but are not limited to, N-dialkyl (meth) acrylamides, such as N, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-dipropyl (meth) acrylamide, and N, N-dibutyl (meth) acrylamide.

Exemplary second monomer units having an amino group include various N, N-dialkylaminoalkyl (meth) acrylates (i.e., monomer units that include a (N, N-dialkylaminoalkyl) -O-group) and N, N-dialkylaminoalkyl (meth) acrylamides (i.e., monomer units that include a (N, N-dialkylaminoalkyl) -N-group). Examples include, but are not limited to: n, N-dimethylaminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylamide, N-dimethylaminopropyl (meth) acrylate, N-dimethylaminopropyl (meth) acrylamide, N-diethylaminoethyl (meth) acrylate, N-diethylaminoethyl (meth) acrylamide, N-diethylaminopropyl (meth) acrylate, and N, N-diethylaminopropyl (meth) acrylamide.

The (meth) acrylate copolymer typically comprises at least 1 wt% of the second monomer unit. Such amounts are generally required to provide the desired hydrogen bonding within the curable (meth) acrylate copolymer. In some examples, the (meth) acrylate copolymer comprises at least 1.5 wt.%, at least 2 wt.%, at least 3 wt.%, at least 4 wt.%, at least 5 wt.%, at least 6 wt.%, at least 7 wt.%, at least 8 wt.%, at least 9 wt.%, or at least 10 wt.% of the second monomer units. The amount of the second monomer unit may be up to 13 wt%. If the (meth) acrylate copolymer contains more than 13% by weight of the second monomer unit, the glass transition temperature may be too high to be used as a pressure-sensitive adhesive. In addition, there may be miscibility problems with other monomers included in the polymerizable composition used to form the (meth) acrylate copolymer. In some examples, the (meth) acrylate copolymer comprises at most 10 wt.%, at most 9 wt.%, at most 8 wt.%, at most 7 wt.%, or at most 6.5 wt.% of the second monomer units. The amount of the second monomer unit is typically in the range of 1 to 13 wt%, 3 to 10 wt%, or 5 to 10 wt%, based on the total weight of the (meth) acrylate copolymer.

The curable (meth) acrylate copolymer further comprises a third monomer unit of formula (III) in an amount ranging from 0.05 to 5 weight percent based on the total weight of monomer units of the curable (meth) acrylate copolymer.

In formula (III), the radical R₁Is the same as defined above, and the group R₃Including 1) aromatic ketone groups that cause hydrogen abstraction from the polymer chain upon exposure to ultraviolet radiation, or 2) (meth) acryloyl groups that undergo free radical polymerization upon exposure to ultraviolet or visible radiation in the presence of a photoinitiator (i.e., pendant (meth) acryloyl groups). The hydrogen abstraction type aromatic ketone groups generally require exposure to ultraviolet radiation to trigger the reaction. The pendant (meth) acrylate groups may react upon exposure to ultraviolet or visible radiation based on the absorbance of the photoinitiator in the ultraviolet and visible regions of the electromagnetic spectrum.

In the third monomer unit of the first type of formula (III), R₃The groups include aromatic ketone groups. When subjected to ultraviolet radiation, the aromatic ketone group can abstract a hydrogen atom from another polymer chain or from another portion of the polymer chain. This abstraction results in the formation of free radicals which can subsequently combine to form crosslinks between polymer chains or within the same polymer chain. In many embodiments, the aromatic ketone group is an aromatic ketone group such as, for example, a derivative of benzophenone, acetophenone, or anthraquinone. Monomers that can produce this type of third monomer unit of formula (III) include, for example, 4- (meth) acryloxybenzophenone, 4- (meth) acryloxyethoxybenzophenone, 4- (meth) acryloxy-4 '-methoxybenzophenone, 4- (meth) acryloxyethoxy-4' -methoxybenzophenone, 4- (meth) acryloxy-4 '-bromobenzophenone, 4-acryloxyethoxy-4' -bromobenzophenone and the like, as well as the monomers described in U.S. Pat. No. 10,189,771(Benson et al).

In a third monomer unit of the second type of formula (III), R₃The group includes a (meth) acryloyl group. Namely, R₃In the ultraviolet or visible radiation and lightA group which is free radically reactive in the presence of an initiator. Curable (meth) acrylate copolymers are generally not prepared directly with the presence of a third monomer unit of this type. Instead, a precursor (meth) acrylate copolymer is initially prepared and then further reacted with an unsaturated reagent compound to introduce pendant formula (meth) acryloyl groups. Typically, introducing pendant formula (meth) acryloyl groups involves either (1) a reaction between a nucleophilic group on the precursor (meth) acrylate copolymer and an electrophilic group on the unsaturated reagent compound (i.e., the unsaturated reagent compound includes both an electrophilic group and a (meth) acryloyl group) or (2) a reaction between an electrophilic group on the precursor (meth) acrylate copolymer and a nucleophilic group on the unsaturated reagent compound (i.e., the unsaturated reagent compound includes both a nucleophilic group and a (meth) acryloyl group). These reactions between nucleophilic and electrophilic groups are typically ring-opening, addition or condensation reactions.

In some embodiments of this second type, the precursor (meth) acrylate copolymer has a hydroxyl (-OH), carboxylic acid (-COOH), or anhydride (-O- (CO) -O-) group. If the precursor (meth) acrylate copolymer has hydroxyl groups, the unsaturated reagent compound typically has carboxylic acid (-COOH), isocyanato (-NCO), epoxy (i.e., oxirane) or anhydride groups in addition to the (meth) acryloyl groups. If the precursor (meth) acrylate copolymer has carboxylic acid groups, the unsaturated reagent compound typically has hydroxyl, amino, epoxy, isocyanato, aziridinyl, azetidinyl or oxazolinyl groups in addition to (meth) acryloyl groups. If the precursor (meth) acrylate copolymer has an anhydride group, the unsaturated reagent compound has a hydroxyl or amine group in addition to the (meth) acryloyl group.

In some examples, the precursor (meth) acrylate copolymer has a carboxylic acid group and the unsaturated reagent compound has an epoxy group. Exemplary unsaturated reagent compounds include, for example, glycidyl (meth) acrylate and 4-hydroxybutyl acrylate glycidyl ether. In other examples, the precursor (meth) acrylate copolymer has an anhydride group and is reacted with an unsaturated reagent compound that is a hydroxy-substituted alkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and the like. In other examples of this second type, the precursor (meth) acrylate copolymer has hydroxyl groups and the unsaturated reagent compound has isocyanate groups and (meth) acryloyl groups. Such unsaturated reagent compounds include, but are not limited to, isocyanatoalkyl (meth) acrylates, such as isocyanatoethyl (meth) acrylate. In applications where the adhesive is used in an article having a metal-containing component, it may be preferred to use a precursor (meth) acrylate copolymer having hydroxyl groups. Hydroxyl groups are less problematic in terms of corrosion than acid groups or anhydride groups.

R of the second type₃The radical may have the formula CH₂＝CHR₁- (CO) -Q-L-, wherein L is a linking group and Q is oxy (-O-) or-NH-. The group L comprises an alkylene group, an arylene group, or a combination thereof, and may optionally further comprise-O-, -O- (CO) -, -NH-, or a combination thereof, depending on the particular precursor (meth) acrylate copolymer and the R reacted to form the (meth) acryloyl group₃Specific unsaturated reagent compounds of the group. In some particular examples, the second type of R₃The radical being H₂C＝CHR₁-(CO)-O-R₆-NH-(CO)-O-R₅-O- (CO) -, by the formula- (CO) -O-R on a precursor (meth) acrylate₅Pendant groups of-OH the formula containing hydroxyl groups and as formula H₂C＝CHR₁-(CO)-O-R₆Unsaturated reagent compounds of isocyanatoalkyl (meth) acrylates of-NCO. Radical R₅And R₆Each independently is an alkylene group, such as an alkylene having 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. R₁Is methyl or hydrogen.

The third monomer unit is typically present in an amount in the range of from 0.05 wt% to 5 wt%, based on the total weight of the (meth) acrylate copolymer. If less than 0.05 wt% is used, the concentration may be too low to ensure that sufficient curing occurs. For example, the concentration may be at least 0.1 weight percent, at least 0.2 weight percent, at least 0.3 weight percent, or at least 0.4 weight percent. However, amounts in excess of 5 wt% can result in reduced adhesive performance for adhesives comprising the cured (meth) acrylate copolymer, and/or increased stress buildup in articles comprising the cured (meth) acrylate copolymer, and/or delamination of the adhesive from the substrate within articles comprising the cured (meth) acrylate copolymer. In addition, if the third monomer unit is of the first type containing an aromatic ketone group, yellowing may occur in the adhesive layer when the equivalent exceeds 5% by weight or even less. For example, the concentration may be at most 4 wt%, at most 3 wt%, at most 2 wt%, at most 1.5 wt%, at most 1 wt%, at most 0.8 wt%, or at most 0.6 wt%. In some embodiments, the amount of the third monomeric unit ranges from 0.1% to 5%, 0.1% to 4%, 0.1% to 3%, 0.1% to 2%, 0.2% to 1.5%, 0.2% to 1%, 0.3% to 5%, 0.3% to 2%, 0.3% to 1%, 0.4% to 2%, or 0.4% to 1% by weight.

Other optional monomer units (4 th monomer unit) may be present in the (meth) acrylate copolymer. Other optional monomer units are typically selected based on compatibility with other monomer units in the (meth) acrylate copolymer. These optional monomer units may also be used to adjust the rheological properties of the (meth) acrylate copolymer, for example to adjust the glass transition temperature or the shear storage modulus (G'). These optional monomer units are also typically selected based on the end use of the curable and/or cured (meth) acrylate copolymer. The optional monomer may enhance the compatibility of the sheath with the core.

Suitable nitrogen-containing monomeric units may include, for example, monomeric units derived from various N-alkyl (meth) acrylamides, and may include N, N-dialkyl (meth) acrylamides, such as N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-dimethyl (meth) acrylamide, and N, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N-octyl (meth) acrylamide. Other monomer units derived from various N, N-dialkylaminoalkyl (meth) acrylates and N, N-dialkylaminoalkyl (meth) acrylamides may be included, such as, for example, N-dimethylaminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylamide, N-dimethylaminopropyl (meth) acrylate, N-dimethylaminopropyl (meth) acrylamide, N-diethylaminoethyl (meth) acrylate, N-diethylaminoethyl (meth) acrylamide, N-diethylaminopropyl (meth) acrylate, and N, N-diethylaminopropyl (meth) acrylamide. Other examples include monomer units derived from N-vinylpyrrolidone, N-morpholino (meth) acrylate, diacetone (meth) acrylamide, and N-vinylcaprolactam.

Other optional monomer units included are monomer units formed from (meth) acrylates having an aromatic group other than formula (I) or formula (III). These monomer units may negatively affect optical clarity and for some applications it may be desirable to control their amount. Exemplary monomers include, but are not limited to, 2-phenoxyethyl acrylate (available under the trade designation SR339 from Sartomer (Exton, PA)), 2- (phenylthio) ethyl acrylate (available from nit industries, Woodland, NJ) (Cytec Ind, japan)), 2-phenylphenoxyethyl acrylate (available from Double Bond Chemical industry, Taiwan, China, Taiwan), and 3-phenoxyphenyl methyl propionate (available from american Chemicals, Co) (milon Chemicals (Korea)).

The amount of any other optional monomer or combination of optional monomers is typically no greater than 20 weight percent based on the total weight of the curable (meth) acrylate copolymer. That is, the amount of other optional monomers is no greater than 15 wt%, no greater than 10 wt%, or no greater than 5 wt%, and, if present, is equal to at least 1 wt%, at least 2 wt%, or at least 5 wt%. The amount may range from 0 wt% to 20 wt%, 1 wt% to 20 wt%, 5 wt% to 20 wt%, 0 wt% to 10 wt%, 1 wt% to 10 wt%, 0 wt% to 5 wt%, or 1 wt% to 5 wt%.

In addition to the monomers used to form the various monomeric units described above, the polymerizable compositions used to prepare the (meth) acrylate copolymers typically include a free radical initiator to initiate polymerization of the monomers. The free radical initiator may be a photoinitiator or a thermal initiator. The amount of free radical initiator is generally in the range of from 0.05 to 5% by weight, based on the total weight of monomers used.

Suitable thermal initiators include various azo compounds such as those commercially available under the tradename VAZO from dupont (Wilmington, DE USA) including VAZO 67, which is 2,2 '-azobis (2-methylbutyronitrile), VAZO 64, which is 2, 2' -azobis (isobutyronitrile), VAZO 52, which is 2,2 '-azobis (2, 4-dimethylvaleronitrile), and VAZO 88, which is 1, 1' -azobis (cyclohexanecarbonitrile); various peroxides, such as benzoyl peroxide, cyclohexane peroxide, lauroyl peroxide, di-t-amyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, and peroxides commercially available under the trade name LUPEROX (e.g., LUPEROX 101 (which is 2, 5-bis (t-butylperoxy) -2, 5-dimethylhexane) and LUPEROX 130 (which is 2, 5-dimethyl-2, 5-di (t-butylperoxy) -3-hexyne)) from the company Atofina chemical (Philadelphia, PA); various hydroperoxides, such as tert-amyl hydroperoxide and tert-butyl hydroperoxide; and mixtures thereof.

In many embodiments, a photoinitiator is used, particularly when a second type of monomeric unit of formula (III) is used. Some exemplary photoinitiators are benzoin ethers (e.g., benzoin methyl ether or benzoin isopropyl ether) or substituted benzoin ethers (e.g., anisoin methyl ether). Other exemplary photoinitiators are substituted acetophenones such as 2, 2-diethoxyacetophenone or 2, 2-dimethoxy-2-phenylacetophenone (commercially available under the trade designation IRGACURE 651 from BASF corp., Florham Park, NJ, USA or ESACURE KB-1 from Sartomer, Exton, PA, USA) of Exton, n. Still other exemplary photoinitiators are substituted alpha-ketols (such as 2-methyl-2-hydroxypropiophenone), aromatic sulfonyl chlorides (such as 2-naphthalenesulfonyl chloride), and photoactive oximes (such as 1-phenyl-1, 2-propanedione-2- (O-ethoxycarbonyl) oxime). Other suitable photoinitiators include, for example: 1-Hydroxycyclohexylphenylketone (commercially available under the trade name IRGACURE 184), bis (2,4, 6-trimethylbenzoyl) phenylphosphine oxide (commercially available under the trade name IRGACURE 819), ethyl 2,4, 6-trimethylbenzoylphenylphosphinate (commercially available under the trade name IRGACURE TPO-L), 1- [4- (2-hydroxyethoxy) phenyl ] -2-hydroxy-2-methyl-1-propan-1-one (commercially available under the trade name IRGACURE 2959), 2-benzyl-2-dimethylamino-1- (4-morpholinylphenyl) butanone (commercially available under the trade name IRGACURE 369), 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinylpropan-1-one (commercially available under the trade name IRGACURE 907) De), and 2-hydroxy-2-methyl-1-phenylpropan-1-one (commercially available under the trade designation DAROCUR 1173 from dedicated Chemicals of soda Chemicals (Tarrytown, NY, USA)).

The polymerizable composition may also optionally comprise a chain transfer agent to control the molecular weight of the resulting (meth) acrylate copolymer. Examples of useful chain transfer agents include, but are not limited to: carbon tetrabromide, alcohols (e.g., ethanol and isopropanol), thiols or thiols (e.g., lauryl mercaptan, butyl mercaptan, t-dodecyl mercaptan, ethanethiol, isooctyl thioglycolate, 2-ethylhexyl mercaptopropionate, ethylene glycol dimercaptoacetate), and mixtures thereof. If used, the polymerizable mixture may contain up to 1 weight percent chain transfer agent based on the total weight of the monomers. The amount can be up to 0.5 wt%, up to 0.3 wt%, up to 0.2 wt%, or up to 0.1 wt%, and is generally equal to at least 0.005 wt%, at least 0.01 wt%, at least 0.05 wt%, or at least 0.1 wt%. For example, the polymerizable composition can comprise 0.005 wt.% to 0.5 wt.%, 0.01 wt.% to 0.5 wt.%, 0.05 wt.% to 0.2 wt.%, 0.01 wt.% to 0.2 wt.%, or 0.01 wt.% to 0.1 wt.% of the chain transfer agent, based on the total weight of the monomers.

The polymerizable composition may also comprise other components such as, for example, antioxidants and/or stabilizers such as hydroquinone monomethyl ether (p-methoxyphenol, MeHQ), and those commercially available under the trade name IRGANOX1010 (tetrakis (methylene (3, 5-di-tert-butyl-4-hydroxyhydrocinnamate)) methane from BASF Corp (Florham Park, NJ., USA). Antioxidants and/or stabilizers may be used to increase the temperature stability of the resulting (meth) acrylate copolymer. Antioxidants and/or stabilizers, if used, are generally used in amounts ranging from 0.01 weight percent (wt.%) to 1.0 wt.%, based on the total weight of monomers in the polymerizable composition.

The polymerization of the polymerizable composition may be carried out in the presence or absence of an organic solvent. If an organic solvent is included in the polymerizable composition, the amount is generally selected to provide the desired viscosity to the polymerizable composition and the polymer composition. Examples of suitable organic solvents include, but are not limited to: methanol, tetrahydrofuran, ethanol, isopropanol, heptane, acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, toluene, xylene, and ethylene glycol alkyl ether. Those solvents may be used alone or in combination. In some embodiments, the organic solvent is present in an amount less than 15 wt-%, less than 10 wt-%, less than 8 wt-%, less than 6 wt-%, less than 5 wt-%, or less than 2 wt-%, based on the total weight of the polymerizable composition. If used, any organic solvent is typically removed at the completion of the polymerization reaction or during coating. In many embodiments, the polymerization is carried out in the presence of little or no organic solvent. I.e., the polymer composition contains no organic solvent or a minimal amount of organic solvent.

Depending on the type of monomer unit of formula (III) used, the curable (meth) acrylate copolymer or precursor (meth) acrylate copolymer may be prepared by any conventional polymerization method, such as solution polymerization or emulsion polymerization, including thermal bulk polymerization under adiabatic conditions, as disclosed in U.S. Pat. nos. 5,637,646(Ellis) and 5,986,011(Ellis et al). Other methods of preparing either type of (meth) acrylate copolymer include continuous free radical polymerization methods as described in U.S. Pat. Nos. 4,619,979 and 4,843,134(Kotnour et al) and polymerization in a polymerization package as described in U.S. Pat. No. 5,804,610(Hamer et al).

The curable (meth) acrylate copolymer has a weight average molecular weight ("Mw") in a range of 100,000 daltons to 1,500,000 daltons ("Da"). If the molecular weight is below 100,000Da, the adhesive may not have suitable creep resistance to maintain a uniform cross-sectional area, as it may tend to sag or slump within the skin. In addition, curable (meth) acrylate copolymers with too low an Mw have shown cold flow, which may be undesirable in some embodiments. Curable (meth) acrylate copolymers with too high an Mw may have too high a melt viscosity to blend with the skin in the dispensing unit, and too long a stress relaxation time to effectively flow and cover various features on a rough substrate. If the molecular weight is below 100,000Da, the amount of third monomer units required to effectively cure the (meth) acrylate copolymer may be quite high. If the amount of the third monomer unit is too high, the curing reaction may proceed too fast. That is, the (meth) acrylate copolymer may change from having no gel content to having a very high gel content (and thus a highly elastomeric cured adhesive composition, which may not be desirable in some applications). The weight average molecular weight is typically at least 125,000Da, at least 150,000Da, at least 175,000Da, at least 200,000Da, at least 225,000Da, at least 250,000Da, or at least 300,000 Da. The molecular weight may be at most 1,500,000Da, at most 1,250,000Da, at most 1,000,000Da, at most 900,000Da, or at most 800,000 Da. In some embodiments, the weight average molecular weight is in the range of 125,000Da to 1,500,000Da, in the range of 100,000Da to 1,250,000Da, in the range of 150,000Da to 1,500,000Da, in the range of 175,000Da to 1,500,000Da, in the range of 200,000Da to 1,500,000Da, in the range of 225,000Da to 1,500,000Da, in the range of 250,000Da to 1,500,000Da, in the range of 300,000Da to 1,500,000 Da. The weight average molecular weight can be determined by gel permeation chromatography ("GPC").

Sheath materials useful in embodiments of the present disclosure generally fall within the class of semi-crystalline polymers. Semi-crystalline polymers can provide robust mechanical properties even at relatively low molecular weights. Thus, suitable semi-crystalline sheath materials may have a weight average molecular weight (Mw) as low as 100,000g/mol and still provide the toughness and elongation necessary to form stable filament spools. However, higher molecular weight polymers generally result in lower MFI values, and thus higher Mw polymers are preferred. Thus, the sheath Mw typically exceeds 150,000g/mol, exceeds 200,000g/mol, exceeds 300,000g/mol, exceeds 400,000g/mol, or even exceeds 500,000 g/mol.

Other monomeric materials having multiple (meth) acryloyl groups may be combined with the curable (meth) acrylate copolymer. These monomers may be added to adjust the crosslink density of the cured (meth) acrylate copolymer. That is, these monomers are typically added to the curable (meth) acrylate copolymer after it is formed. These monomers can react with the pendant (meth) acryloyl groups of the curable (meth) acrylate copolymer when exposed to ultraviolet or visible radiation in the presence of a photoinitiator. If added, the amount of these monomeric materials is typically in the range of 0 to 30 parts per hundred ("pph"), based on the weight of the curable (meth) acrylate copolymer. For example, the amount may be at least 1pph, at least 2pph, or at least 5pph, and may be at most 30pph, at most 25pph, at most 20pph, at most 15pph, or at most 10 pph.

Exemplary monomers having two (meth) acryloyl groups include 1, 2-ethanediol diacrylate, 1, 3-propanediol diacrylate, 1, 9-nonanediol diacrylate, 1, 12-dodecanediol diacrylate, 1, 4-butanediol diacrylate, 1, 6-hexanediol diacrylate, butanediol diacrylate, bisphenol a diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate (e.g., available from sartomer under the tradenames SR-210, SR-252, and SR-603), polypropylene glycol diacrylate, polyethylene/polypropylene diacrylate copolymer, hydroxypivalyl hydroxypivalate modified caprolactone diacrylate, and polyurethane diacrylate (e.g., available from sartomer under the trade names CN9018 and CN 983).

Exemplary monomers having three or four (meth) acryloyl groups include, but are not limited to, trimethylolpropane triacrylate (e.g., commercially available under the trade designation TMPTA-N from Surface Specialties, Smyrna, GA, and SR-351 from Sartomer, Exton, PA, Exton), pentaerythritol triacrylate (e.g., commercially available under the trade designation SR-444 from Sartomer), a mixture of tris (2-hydroxyethyl isocyanurate) triacrylate (e.g., commercially available under the trade designation SR-368 from Sartomer), pentaerythritol triacrylate, and pentaerythritol tetraacrylate (e.g., commercially available under the trade designation PETIA (the ratio of tetraacrylate to triacrylate is about 1:1), and PETA-K (the ratio of tetraacrylate to triacrylate is about 3:1) Commercially available from specialty surface technology corporation), pentaerythritol tetraacrylate (e.g., commercially available from sartomer under the trade name SR-295), di-trimethylolpropane tetraacrylate (e.g., commercially available from sartomer under the trade name SR-355), and ethoxylated pentaerythritol tetraacrylate (e.g., commercially available from sartomer under the trade name SR-494). Exemplary crosslinking agents having five (meth) acryloyl groups include, but are not limited to, dipentaerythritol pentaacrylate (e.g., commercially available from sartomer under the trade name SR-399).

The curable (meth) acrylate copolymer is typically tacky (i.e., the curable (meth) acrylate copolymer is tacky prior to curing with ultraviolet or visible radiation; in many cases, the cured (meth) acrylate copolymer is also tacky). If desired, a tackifier may be added to the curable (meth) acrylate copolymer (or to the mixture of monomers prior to forming the curable (meth) acrylate copolymer). Useful tackifiers include, for example, rosin ester resins, aromatic hydrocarbon resins, aliphatic hydrocarbon resins, and terpene resins. Generally, light colored tackifiers selected from hydrogenated rosin esters, hydrogenated terpenes, or hydrogenated aromatic hydrocarbon resins are preferred.

Low molecular weight (e.g., weight average molecular weight of 100,000Da or less as determined by Gel Permeation Chromatography (GPC)) and high glass transition temperature (e.g., greater than 30 ℃) polymers derived from (meth) acrylates can be combined with the (meth) acrylate copolymers. Suitable low molecular weight polymers are described, for example, in U.S. Pat. Nos. 6,783,850(Takizawa et al), 6,448,339(Tomita), 4,912,169(Whitmire et al) and 6,939,911(Tosaki et al). These polymers are useful as tackifiers.

The tackifier is typically selected to be miscible with the (meth) acrylate copolymer. Either solid or liquid tackifiers may be added. Solid tackifiers typically have a number average molecular weight (Mn) of 10,000 grams per mole or less and a softening point above about 70 ℃. The liquid tackifier is a tacky material having a softening point of about 0 ℃ to about 70 ℃.

Suitable tackifying resins include rosin resins such as rosin acids and their derivatives (e.g., rosin esters); terpene resins such as polyterpenes (e.g., alpha-pinene-based resins, beta-pinene-based resins, and limonene-based resins) and aromatic-modified polyterpene resins (e.g., phenol-modified polyterpene resins); a coumarone-indene resin; and petroleum-based hydrocarbon resins such as C5-based hydrocarbon resins, C9-based hydrocarbon resins, C5/C9-based hydrocarbon resins, and dicyclopentadiene-based resins. These tackifying resins (if added) may be hydrogenated to reduce their color impact on the pressure sensitive adhesive composition. Combinations of various tackifiers may be used if desired. In many embodiments, the tackifier is or comprises a rosin ester.

Rosin ester tackifiers are the reaction products of various rosin acids and alcohols. These include, but are not limited to: methyl esters of rosin acids, triethylene glycol esters of rosin acids, glycerol esters of rosin acids, and pentaerythritol esters of rosin acids. These rosin esters can be partially or fully hydrogenated to improve stability and reduce the effect of their color on the pressure sensitive adhesive composition. Rosin resin tackifiers are commercially available, for example, from Eastman Chemical Company (Kingsport, TN, USA) of kingdom porter, tennessee, USA under the trade names PERMALYN, stayblite, and FORAL, and from Newport Industries, London, England, in the united kingdom under the trade names NUROZ and NUTAC. Fully hydrogenated rosin resins are commercially available, for example, from Istman chemical under the trade name FORAL AX-E. Partially hydrogenated rosin resins are commercially available from Istman chemical company under the trade name STAYBELITE-E, for example.

Plasticizers can also be used to adjust the rheology of the adhesive composition. The plasticizer may be a non-reactive compound such as phosphate esters, adipate esters, and phthalate esters. Various low glass transition temperature (e.g., below 0 ℃), lower molecular weight (e.g., Mw below 100,000 daltons as determined by GPC) acrylic polymers prepared similarly to the acrylic tackifiers described above can also be used as plasticizers.

Other optional additives include, for example, antioxidants, UV stabilizers, UV absorbers, pigments, curing agents, ionic crosslinking agents, antiblocking agents, and polymeric additives. These other optional additives may be selected, if desired, so that they do not significantly reduce the optical clarity or other desired performance attributes of the adhesive composition.

Ionic crosslinkers useful in embodiments of the present disclosure include, for example, zinc oxide, zinc abietate (also known as "resinates"), zinc stearate, sodium acetate, and 2EHA/DMAEMA (40/60) copolymers prepared as described in U.S. Pat. No. 5,986,011(Ellis et al).

Antiblocking agents are particularly useful in the outer layers of polyethylene to prevent layer-to-layer sticking or adhesion of the polyethylene when the extruded film is wound into a roll. Useful materials include diatomaceous earth (alone or in a low density polyethylene binder). Antiblocking agents may be included in amounts of about 1% to about 20% and preferably about 3% to about 8% by weight of the polyethylene resin. Particularly useful antiblocking agents are: POLYFIL ABC 5000, available from Polyfil corporation of Rockwell, N.J. (Polyfil corporation, Rockaway, N.J.).

The curable (meth) acrylate copolymer (or curable adhesive comprising the curable (meth) acrylate copolymer) may be cured to form a cured (meth) acrylate (or cured adhesive comprising the cured (meth) acrylate copolymer). In some embodiments, the curable (meth) acrylate copolymer or curable adhesive composition may be in the form of a layer (e.g., a film) that can be stored or shipped for later curing by a customer. That is, hydrogen bonding within the curable (meth) acrylate copolymer increases cohesive strength of the curable (meth) acrylate copolymer (or curable adhesive composition). This cohesive strength enhances the dimensional stability of the filaments and reduces the tendency to flow if the temperature is near room temperature or below 40 ℃.

The curable (meth) acrylate copolymer and/or related curable adhesive composition combine the properties of high flowability required during hot melt processing (e.g., typically conducted at elevated temperatures such as 100 ℃ to 200 ℃ or preferably 150 ℃ to 175 ℃) with the dimensional stability and cohesive strength (typically at temperatures in the range of about room temperature to less than 65 ℃) required to store and/or transport the filaments to the end user. Cohesive strength allows film-like behavior at room temperature while maintaining high viscosity characteristics (and thus low elasticity and short stress relaxation times) at elevated temperatures for hot melt dispensing. Advantageously, the adhesive filaments may have good dimensional stability when stored at room temperature and do not require refrigeration to maintain dimensional stability.

Printing and curing method

A method of printing and curing a hot melt processable adhesive is provided. The method includes forming a sheath-core filament as described above. The method further includes melting the sheath-core filament and blending the sheath with the core to form a molten composition. The method further comprises dispensing the molten composition through a nozzle onto a substrate. The molten composition may be formed prior to reaching the nozzle, may be formed by mixing in the nozzle, or may be formed during dispensing through the nozzle, or a combination thereof. Preferably, the sheath composition is homogeneously blended throughout the core composition. The method further includes curing the molten composition by receiving actinic radiation, i.e., UV and/or visible light, after dispensing the molten composition onto the substrate.

Melt filament fabrication ("FFF"), also known under the trade designation "FUSED position molding" from stretasy, inc, Eden Prairie, minn, of idenproli, minn, is a process that uses thermoplastic strands fed through a heat box to produce a molten aliquot of material from an extrusion head. The extrusion head extrudes a bead of material in 3D space as required by a plan or drawing (e.g., a computer aided drawing ("CAD") file). The extrusion head typically lays down the material in layers and after the material is deposited, it fuses.

One suitable method for printing sheath-core filaments comprising adhesive onto a substrate is a continuous, non-pumping, filament-fed dispensing unit. In this method, the dispensing throughput is regulated by the linear feed rate of the sheath-core filament admitted to the dispensing head. In most currently commercially available FFF dispensing heads, unheated filaments are mechanically pushed into a heating zone, which provides sufficient force to push the filaments out of the nozzle. A variation of this method is to incorporate a conveying screw in the heating zone that is used to pull the filaments from the spool and also to create pressure to dispense the material through the nozzle. While adding a conveying screw to the dispensing head increases cost and complexity, this does increase throughput and gain the opportunity to mix and/or blend the desired level of components. A characteristic of filament feed dispensing is that it is a truly continuous process, with only one short length of filament at any given point in the dispensing head.

There may be several benefits to the filament feed dispensing method compared to traditional hot melt adhesive deposition methods. First, the filament feed dispensing method generally allows for faster switching to a different adhesive. Moreover, these methods do not operate in a semi-batch mode with the melt tank, and this minimizes the chance of thermal degradation of the adhesive and associated defects in the deposited adhesive. The filament feed dispensing process may use materials with higher melt viscosities, which provide adhesive beads that can be deposited with greater geometric accuracy and stability without the need for a separate curing or crosslinking step. In addition, higher molecular weight raw materials may be used in the adhesive due to higher allowable melt viscosity. This is advantageous because uncured hot melt pressure sensitive adhesives containing higher molecular weight raw materials can have significantly improved high temperature holding power while maintaining stress dissipation capability.

The form factor of FFF filaments is often a concern. For example, the consistent cross-sectional shape and longest cross-sectional distance (e.g., diameter) contribute to the cross-compatibility of the sheath-core filament with existing standardized FFF filaments such as ABS or polylactic acid (PLA). In addition, because the FFF dispensing rate is typically determined by the feed rate of the linear length of the filaments, a consistent longest cross-sectional distance (e.g., diameter) helps ensure that the adhesive has the correct throughput. When used in FFF, suitable longest cross-sectional distance variations of a sheath-core filament in accordance with at least certain embodiments include a maximum variation of 20% over a 50cm length, or even a maximum variation of 15% over a 50cm length.

Extrusion-based layered deposition systems (e.g., melt filament processing systems) can be used to prepare articles comprising a printing adhesive in the methods of the present disclosure. Deposition systems are commercially available having a variety of extrusion types including single screw extruders, twin screw extruders, hot end extruders (e.g., for filament feed systems), and direct drive hot end extruders (e.g., for elastomeric filament feed systems). The deposition system may also have different motion types for material deposition, including the use of XYZ stages, gantry cranes, and robotic arms. Common manufacturers of Additive manufacturing deposition systems include sterasis corporation (Stratasys), alemter corporation (Ultimaker), mackert corporation (MakerBot), wolf corporation (Airwolf), WASP, markfreund corporation (markformed), pulusian corporation (Prusa), lultzbot corporation (Lulzbot), biglep corporation (BigRep), cos Additive corporation (cosi Additive), and sincinti Incorporated. Suitable commercially available deposition systems include, for example, but are not limited to: BAAM, which has a pellet feed screw extruder and a gantry type motion type, available from Cincinnati Incorporated (Harrison, OH); BETABRAM model P1, which has a pressurized paste extruder and a gantry type motion type, available from intelab d.o.o. (Senovo, Slovenia) engleribe (schwannieia); AM1, having a pellet feed screw extruder or a geared filament extruder and XYZ stage motion type, available from costas Additive Inc (Houston, TX); a KUKA robot having a robotic arm motion type available from Kuka (Sterling Heights, MI); and AXIOM, which has a geared filament extruder and XYZ stage motion types, available from sirius 3D (Fountain Valley, california) (AirWolf 3D (CA)).

Three-dimensional articles comprising printed adhesives can be made from computer-aided drafting ("CAD") models, for example, in a layer-by-layer manner by extruding molten adhesive onto a substrate. Movement of the extrusion head relative to the substrate (onto which the adhesive is extruded) is performed under computer control in accordance with build data representative of the final article. The build data is obtained by initially slicing a CAD model of the three-dimensional article into a plurality of horizontally sliced layers. Then, for each sliced layer, the host computer generates a build path for obtaining a deposited road of the composition to form a three-dimensional article having a printed adhesive thereon. In selected embodiments, the print adhesive includes at least one groove formed on a surface of the print adhesive. Optionally, the printing adhesive forms a discontinuous pattern on the substrate.

The substrate on which the molten adhesive is deposited is not particularly limited. In many embodiments, the substrate comprises a polymeric component, a glass component, or a metal component. The use of additive manufacturing to print an adhesive on a substrate can be particularly advantageous when the substrate has a non-planar surface (e.g., a substrate having an irregular or complex surface topography).

The sheath-core filaments may be extruded through a nozzle carried by an extrusion head and deposited in a series of roads on a substrate in the x-y plane. The exiting molten adhesive fuses with the previously deposited molten adhesive as it solidifies upon a drop in temperature. This may provide at least a portion of the printed adhesive. The position of the extrusion head relative to the substrate is then incremented along the z-axis (perpendicular to the x-y plane) and the process is repeated to form at least a second layer of molten adhesive on at least a portion of the first layer. Changing the position of the extrusion head relative to the deposited layer may be performed, for example, by lowering the substrate on which the layer is deposited. This process can be repeated as many times as necessary to form a three-dimensional article similar to a CAD model that contains a printed adhesive. Further details can be found, for example, in Turner, b.n. et al, "review of melt extrusion additive manufacturing processes: I. process design and modeling "; rapid Prototyping Journal20/3(2014)192-204 ("A review of melt additive manufacturing processes: I. process design and modeling"; Rapid Prototyping Journal20/3(2014) 192-204). In certain embodiments, the print adhesive comprises an overall shape that varies in thickness on an axis orthogonal to the substrate. This is particularly advantageous where it is desired that the adhesive shape cannot be formed using die cutting of the adhesive. In some embodiments, it may be desirable to apply only a single adhesive layer, as this may be advantageous, for example, to minimize material usage and/or reduce the size of the final bond line.

A variety of molten filament manufacturing 3D printers may be used to implement the methods according to the present disclosure. Many of these are commercially available under the trade designation "FDM" from stulatas corporation (Stratasys, inc., Eden Prairie, MN) and its affiliates, of the Eden steppe, minnesota. Desktop 3D printers for creative and design development and large printers for direct digital manufacturing are available from stratlas corporation (Stratasys) and its subsidiaries, as for example under the trade names "MAKERBOT replight", "upgrade", "MOJO", "medium and" FORTUS ". Other 3D printers for melt filament manufacturing are commercially available from, for example, 3D Systems, Rock Hill, SC, and air wolf 3D, Costa Mesa, CA, of corkemel, south carolina.

In certain embodiments, the method further comprises mixing (e.g., mechanically) the molten composition prior to dispensing the molten composition. In other embodiments, the process of melting in the nozzle and dispensing through the nozzle can provide sufficient mixing to the composition such that the molten composition mixes in the nozzle, passes through the nozzle during dispensing, or both.

The temperature of the substrate on which the adhesive may be deposited may also be adjusted to promote melting of the deposited adhesive. In the methods according to the present disclosure, the temperature of the substrate can be, for example, at least about 100 ℃, 110 ℃, 120 ℃, 130 ℃, or 140 ℃ up to 175 ℃ or 150 ℃.

The method by which the dispensed adhesive is curable is not particularly limited. The adhesive may be cured with any actinic radiation by methods known to those of ordinary skill in the relevant art. Suitable LED light sources include, for example, but are not limited to, Phoson, 365nm UV-LED FJ100 (available from Phoson Technology Hillsboro, OR) of Hillsboro, Oreg.). Suitable mercury Light sources include, for example, Light Hammer LHC10 Mark2 fusion lamp system equipped with a D-bulb (available from herley Noblelight America LLC Gaithersburg, Maryland, inc.). Although many light sources are available, the duration of acceptance is only in joules/cm received by the adhesive²Is the ultimate dose limit of the unit. For example, the LED source may have a width of 6W/cm²So we will only require a cure time of a few hundred milliseconds to achieve the desired dose of 500mJ/cm 2. In some embodiments, the cured adhesive composition may be formed after exposure to ultraviolet or visible radiation for less than 10 seconds, less than 5 seconds, or less than 2 seconds.

Printed adhesives prepared by methods according to the present disclosure may be articles useful in various industries, for example, the aerospace, apparel, construction, automotive, business machine products, consumer, defense, dental, electronics, educational, heavy equipment, jewelry, medical, and toy industries. The composition of the sheath and core can be selected so that the printing adhesive is transparent if desired.

Selected embodiments of the present disclosure

In a first embodiment, there is provided a sheath-core filament comprising:

Wherein

R₁Is hydrogen or methyl; and is

R₂Is an alkyl, heteroalkyl, aryl, aralkyl or alkaryl group;

Wherein

R₁Is hydrogen or methyl; and is

Wherein

In a second embodiment, a sheath-core filament of the first embodiment is provided, wherein the non-adherent sheath comprises a polymer selected from the group consisting of (meth) acrylic block copolymers, ethylene methyl copolymers, and combinations thereof.

In a third embodiment, there is provided the sheath-core filament of the first or second embodiment wherein 1% to 10% of the longest cross-sectional distance of the sheath-core filament is sheath and 90% to 99% of the longest cross-sectional distance of the sheath-core filament is core.

In a fourth embodiment, there is provided the sheath-core filament of any one of the first to third embodiments, wherein the curable (meth) acrylate copolymer has a weight average molecular weight in the range of 200kDa to 1500 kDa.

In a fifth embodiment, there is provided the sheath-core filament of any one of the first to fourth embodiments, wherein the curable adhesive composition further comprises an ionic crosslinking additive.

In a sixth embodiment, there is provided the sheath-core filament of any one of the first to fifth embodiments, the cured adhesive composition being a reaction product resulting from subjecting the sheath-core filament to ultraviolet or visible light radiation after compounding the sheath-core filament through a heated extruder nozzle.

In a seventh embodiment, a sheath-core filament of the sixth embodiment is provided, wherein the cured adhesive composition exhibits a creep resistance of greater than 3MPa-s, greater than 5MPa-s, or greater than 8MPa-s when tested according to the creep resistance test method.

In an eighth embodiment, a sixth implementation is providedThe sheath-core filament of embodiment or the seventh embodiment, wherein the cured adhesive composition is capable of forming a filament at room temperature of 323mm²A shear force of 1kg for at least 100 minutes, at least 1000 minutes, or at least 5000 minutes was maintained on the stainless steel panel.

In a ninth embodiment, there is provided the sheath-core filament of any one of the sixth to eighth embodiments, wherein the cured adhesive composition exhibits a peel adhesion to stainless steel of at least 30N/cm when tested according to the 180 ° peel test method.

In a tenth embodiment, there is provided the sheath-core filament of any one of the sixth to ninth embodiments, wherein the cured adhesive composition is formed after exposure to ultraviolet or visible radiation for less than 10 seconds, less than 5 seconds, or less than 2 seconds.

In an eleventh embodiment, an article is provided that includes a first substrate, a second substrate, and a layer of the cured adhesive composition of any one of the sixth to tenth embodiments, wherein the layer of the cured adhesive composition is positioned between the first substrate and the second substrate.

In a twelfth embodiment, there is provided a method of making a sheath-core filament, the method comprising:

a) forming a core composition comprising the curable binder composition of the first embodiment;

c) wrapping the sheath composition around the core composition to obtain the sheath-core filament, wherein the sheath-core filament has an average longest cross-sectional distance in a range of 1 millimeter to 20 millimeters.

In a thirteenth embodiment, there is provided the method of the twelfth embodiment, wherein wrapping the skin composition around the core composition comprises co-extruding the core composition and the skin composition such that the skin composition surrounds the core composition.

Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

Examples

All parts, percentages, ratios, and the like in the examples and the remainder of the specification are by weight unless otherwise indicated. Unless otherwise indicated, all other reagents were obtained or purchased from fine chemical suppliers such as Sigma Aldrich Company of st. The following abbreviations are used in this section: min is min, s is sec, g is g, mg is mg, kg is kg, m is m, cm, mm is mm, μm is μm or μm, c is degrees celsius, f is degrees fahrenheit, N is newton, oz, Pa is pascal, MPa is MPa, rpm is rpm, phh is per hundred, psi is pressure/square inch, cc/rev is cubic centimeter/revolution, cm is rev³Cubic foot-centimeter

Table 1 (below) lists the materials used in the examples and their sources.

Table 1: material List

Test program

Melt flow index test method for all samples

Melt Flow Index (MFI) measurements were carried out on all samples according to the Method described in ASTM D1238-13 ("Standard Test Method for Melt Flow Rates of Thermoplastics" the latest revision 2013, procedure A for extruded plastomers). The equipment used was a Tinius Olsen MP 987 extrusion plastometer (melt index meter) with standard die sizes for procedure a. The test conditions were a temperature of 190 ℃ and a weight of 2.16 kg. A total of 8-19 replicates were performed to determine statistical data, i.e. mean MFI (in g/10min), standard deviation of MFI and 95% confidence interval on the mean.

Melt flow index literature method

The MFI literature method is reported as ASTM D1238-13, which has a 2.16kg load and is measured at 190 ℃, and those values are expected to be directly comparable to the test MFI values reported in the results section of table 4 below.

Method for calculating melt flow index of polymer blend from homopolymer melt flow index

The MFI of the polymer blend can be approximated as:

log(MFI_{finally, the product is processed})＝X₁*log(MFI ₁)+X₂*log(MFI₂)

Wherein X₁And X₂Is the weight fraction X of each polymer_iAnd MFI₁And MFI₂Melt flow index of the MFI of the original polymer. The results of such calculations are shown in table 2 below.

TABLE 2 MFI approximation

Creep resistance test method

The examples were analyzed using a DHR-3 parallel plate rheometer equipped with a Peltier plate attachment (TA Instruments, New Castle, DE, USA) to characterize the creep characteristics of each sample as a function of time.the rheological samples formed an approximately 1mm thick adhesive film between the silicone coated release liners.the samples were then punched out with an 8mm circular die, removed from the release liner, centered on an 8mm diameter parallel plate upper fixture of the rheometer, and compressed down to the Peltier plate until the edge of the sample coincided with the edge of the top plate.

The sample was conditioned at a test initiation temperature of 25 ℃ for 120 seconds with a sensitivity of +/-30g under an axial force control of 40g, and then no axial force conditioning was performed to maintain the plate at a fixed gap for the remainder of the test. A holding stress of 1860 seconds at 8,000Pa was then applied. Although many physical parameters of the material were recorded during creep testing, compliance (J) was of primary importance in the characterization of the copolymers of the present invention.

The creep resistance of a polymer is a term used to describe the long-term creep behavior of a material, and the viscosity (Pa-s) is obtained by measuring the slope of compliance versus time and taking the inverse of that value. It is calculated at the completion of the test by extracting compliance values at about 20 minutes (1199.5 seconds) and about 30 minutes (1795.1 seconds) according to the following formula:

creep resistance

[ (compliance at 1795s (1/Pa) -compliance at 1199s (1/Pa)) + (1795s-1199s) ] ^ -1 shear strength test method

The shear test was performed using 12.7mm wide tape prepared in the examples. Stainless steel ("SS") panels were cleaned by wiping (first with heptane, then with acetone) and dried. The adhesive tapes were applied to the panel such that a 12.7mm by 25.4mm portion of each adhesive tape was in firm contact with the panel and a trailing end portion of each adhesive tape was free (e.g., unattached to the panel). The panel with the adhesive tape adhered thereto was fixed in a holder such that the panel formed a 180 ° angle with the extended free end, and a 1kg weight was attached to the free end. The test was conducted under controlled temperature and humidity conditions (72 ° f 50% relative humidity) and the time taken for each tape to separate from the test panel was recorded as the shear strength in minutes. Three shear tests were performed on each adhesive sample and the results were averaged.

D-bulb curing method

PSA film samples were cured at room temperature using a Light Hammer LHC10 Mark2 fusion lamp system equipped with a D-bulb (available from heirlich special Light source, llc, gaithersburg, md). UV dose was measured in the UV-B range using EIT UV Power Puck II (EIT, Sterling, Va.) from Stirling, Va., and linear velocity was adjusted to obtain 500mJ/cm²Desired dosage of UV-B. The adhesive is then open cured under these optimized conditions.

180-degree SS stripping test method

Peel adhesion was measured using an adhesive tape prepared as described below. Stainless steel ("SS") panels were cleaned by wiping (first with heptane, then with acetone) and dried. An adhesive tape measuring 12.7mm wide by 10 to 12cm long was adhered to the panel by rolling 2 times with a 2kg hard rubber roller. The free end of the adhesive tape was folded in half so that the removal angle was 180 ° and attached to the cross-arm of an adhesion tester scale (slip/peel tester, available from instruments inc. strongsville, OH, USA). The stainless steel panel was attached to a platform that moved away from the scale at 12 inches/minute (30.5 cm/minute). The peel test was started 20 minutes after the tape was applied to the test panel, allowing a dwell time for the adhesive to build. The first 2 seconds of each measurement were discarded and the average peel force during the next 5 second peel test was recorded in ounces per width of the adhesive tape sample (ounces/0.5 inch). Three peel tests were performed for each sample and averaged to give the peel force value reported in N/cm.

180-degree glass peeling test method

Peel adhesion was also tested on the air side of float glass panels (sometimes referred to as soda lime glass) available from northwest glass company (friedri, mn). The samples were tested following the same procedure as the SS panel. Three peel tests were performed for each sample and averaged to give the peel force value reported in N/cm.

Optical haze test

Haze was measured in transmission mode using a spectrophotometer (Ultrascan PRO spectrophotometer, available from Hunter Association Laboratory Incorporated, Reston, VA, USA, Reston, USA). An approximately 150 micron thick sample of adhesive coated between release-coated carrier liners was cut to approximately 5cm long by 10cm long. One of the carrier liners was removed and the sample was laminated to a transparent sheet of 69.2mm x 123.2mm x 0.5mm EAGLE XG glass using hand pressure and ensuring that no air bubbles were trapped. The other liner was then removed and a1 mil layer of optically clear PET (available from SKC corporation, atlanta, georgia, usa under the trade designation "SKYROL SH-81") was laminated to the adhesive. The samples were placed in an ultrascan pro spectrophotometer (hunter laboratories, reston, virginia) to measure the transmission through the PET/OCA/glass subassembly.

All core compositions, i.e., cores 1 through 6(C1 through C6), are summarized in table 2, prepared as follows.

Core 1(C1) synthesis: preparation of cores for examples 1-3(EX1-EX3), examples 6-13(EX6-EX13) and comparative example 1(CE1)

The following components were added to a 1.8 liter stainless steel reactor: 900.0 grams IOA, 100.0 grams AA, 0.99 grams AeBP, 1.0 grams IRGANOX1010 antioxidant, 0.76 grams IOTG, 0.006 grams VAZO 52, and 0.2 grams MEHQ. The mixture was heated to 60 ℃ with stirring. The reactor was purged with oxygen while heating and pressurizing with 5psi of nitrogen, and before reaching an initiation temperature of 60 ℃. The polymerization reaction was continued under adiabatic conditions to a peak reaction temperature of 121 ℃. The mixture was cooled to 60 ℃ and 0.228 grams of IOTG, 0.0375 grams of VAZO 52, and 1.25 grams of AeBP were added. The reactor was purged of oxygen and pressurized with 5psi nitrogen. The polymerization reaction was continued under adiabatic conditions to a peak reaction temperature of 145 ℃. The mixture was cooled to 110 ℃ and 0.2 g VAZO 88, 0.03 g Lupersol 101 and 0.375 g AeBP were added. The reactor was purged of oxygen and pressurized with 5psi nitrogen. The polymerization reaction was continued under adiabatic conditions to a peak reaction temperature of 155 deg.C

Core 2(C2) synthesis:the material for core 2 was prepared as described in synthetic example S1 of U.S. patent publication 2013/0184394(Satrijo et al) except that the composition was as follows: 29.7 parts 2EHA, 51 parts BA, 18.5 parts MA, 0.8 parts AA, 0.38pph ABP, 0.15pph IRGACURE 651, 0.4pph IRGANOX 176 and 0.030pph IOTG. The amounts in weight% of the composition are also shown in table 3. Preparation of the core for example 4(EX 4).

Core 3(C3) Synthesis: core 3 was prepared in the same manner as core 2, but using the amounts shown in table 2. Preparation of the core for example 5(EX5)

Core 4(C4) Synthesis: core 4 was prepared in the same manner as core 2, but using the amounts shown in table 2. Preparation of cores for examples 14-15(EX14-15)

Core 5(C5) Synthesis: core 5 was prepared in the same manner as core 2, but using the amounts shown in table 2. Preparation of cores for examples 16-17(EX16-17)

Core 6(C6) Synthesis: core 6 was prepared in the same manner as core 2, but using the amounts shown in table 2. Preparation of cores for examples 18-20(EX 18-20).

Examples 1-20(EX1-E20) and comparative examples 1-5(CE1-CE5) are summarized in Table 4 and prepared as follows.

Sheath-core filament preparation method 1: examples 6 to 9(EX6-EX9)

Sheath-core filaments were prepared by co-extruding a non-tacky outer sheath around an inner PSA core, with exemplary compositions described in table 4 below. For all samples, The PSA cores were compounded using an 18mm co-rotating twin screw extruder (available from copentagart, Germany) (copenian GmbH (Stuttgart, Germany)) at a speed of 200rpm, with all zones heated between 160 ℃ and 170 ℃, The PSA cores were fed as cut pieces into a 50.8mm single screw extruder (available from Bonnot Corporation (Akron, OH)) and The melt stream was metered using a 3cc/rev gear pump (available from korea french press (compute Corporation, anapolis Junction, MD)) and a 19.1mm single screw extruder (HAAKE brand, available from Fisher Scientific Corporation (fischerson, inc.) with a viscous fischery skin (wallichem) and a non-coaxial melt stream outlet of 12mm diameter, similar to the die described in U.S. patent 7,773,834(Ouderkirk et al). Feeding the PSA into an inner core layer of a coaxial die and the non-tacky skin material into an outer skin of the die; ultimately producing a sheath-core filament. The filaments were drawn to a final diameter of 8mm by a water bath at room temperature (22 ℃). The filaments were wound on 75mm diameter tubes for storage.

Sheath-core filament preparation method 2: examples 18-20(EX18-EX20) and comparative examples 2-5(CE2-CE5)

Sheath-core filaments were prepared by co-extruding a non-tacky outer sheath around an inner PSA core, with exemplary compositions described in table 4 below. For all samples, the PSA cores were compounded at a speed of 200rpm using a 25mm co-rotating twin screw extruder (available from claus maffei Berstorff GmbH (Munich, Germany)) with all zones heated between 160 ℃ and 170 ℃, the PSA cores were fed into a 50.8mm single screw extruder (available from bonott company (akron, ohio)) and the melt streams were metered using a 3cc/rev gear pump (available from kels company (atlanta hub), 19.1mm single screw extruder (Killion brand, now available from victims standards company (cavi, inc.) was melted and extruded into non-viscous skins, two melt streams were fed into a coaxial die with exit diameters of 12mm, similar to the internal PSA die described in the okurk patent 7,773,834, while feeding a non-tacky skin material into the outer skin of the die; ultimately producing a sheath-core filament. The filaments were drawn to a final diameter of 8mm by a water bath at room temperature (22 ℃). The filaments were wound on 75mm diameter tubes for storage.

Sheath-core filament preparation method 2: examples 1-5(EX1-EX5) and examples 10-13(EX10-EX13)

Films of non-tacky skins were prepared by hot melt pressing pellets of LPDE (or other film former) to an average thickness of 7-10 mils (0.1778-0.254mm) in a model 4389 hot press (kaver, inc., Wabash, of walbash) at 140 ℃ (284 ° f). Rectangular films with a width of 1.5 inches (3.77cm) and a length of 2.7-5.9 inches (7-15cm) were cut and manually rolled up to wrap around the hot melt PSA formulation to produce core/sheath filaments with a diameter of 12 mm.

Sheath-core filament compounding: examples 6-9(EX6-EX9), examples 18-20(EX18-EX20) and comparative examples 2-5(CE2-CE5)

Batch preparation of core-sheath filament adhesives Intelli-Torque Plastic-Corder Unit (Brabender GmbH from Brabender GmbH, Duisburg, ed.49-5547051, group of Brabender&Kg kultursta β e 49-5547051 Duisburg)), equipped with a capacity of about 55cm³An electrically heated three-part mixer and high shear counter-rotating blades. The mixer was preheated to 150 ℃ and set at a mixing speed of 60rpm, and the core/sheath filaments were added directly to the top of the mixing drum as three individual filaments totaling 50 g. The mixing operation was carried out for 5 minutes, at which time the mixture appeared homogeneous and transparent. After removal from the mixer, the monolith was dissolved at 50% solids in MEK, coated onto a silicone release liner under a notched bar set at a 12 mil (0.3048mm) gap, and dried at 70 ℃ for 20 minutes.

Extruding sheath-core filaments: examples 6-9(EX6-EX9), examples 18-20(EX18-EX20) and comparative examples 2-5(CE2-CE5)

The extruded sheath-core filament compositions were compounded using a ZE30R co-rotating twin screw extruder (krauss maffei Berstorff, Hanover, Germany) and mixed for 3 minutes at 220 rpm. The Nordson Xaloy042709 gear pump was turned at 20rpm to pump the molten adhesive through a heated hose and a die. The die had a gap of 1mm and a width of 101 mm. The extruder, hose and die temperatures were set at 182 ℃. The PSA was extruded onto a 0.075mm thick polyester liner with a different silicone release layer and rolled up until used for testing. The polyester liner was pulled through the die at 244mm/min to produce an adhesive thickness of 1 mm.

Table 4: compositions of examples (EX1-EX13 and EX18-EX20) and comparative examples (CE1-CE5)

Results

Melt flow index value of sheath material

Table 5 shows the results of the melt flow index values of the sheath materials used in EX1-EX20 and CE 1.

Table 5: melt flow index value of sheath material

Leather	MFI process	MFI(g/10min)
			Elvaloy 1224	Literature value	2.0
Bynel 21E533	Literature value	7.3
			Bynel 30E753	Literature value	2.1
Elvaloy 1609	Literature value	6.0
			Nucrel 3990	Literature value	10.0
Elvaloy 1330	Literature value	3.0
			NA217000LDPE	Literature value	5.6
Elvax 3135SB	Literature value	0.4
			LA2250	Test value	22.7
LA4285	Test value	1.8
			50/50LA2250/LA4285 blend	Calculated value	6.5
67/33LA2250/LA 4285 blend	Calculated value	9.9

Creep resistance of sheath-core filament materials

Table 6 shows the results of creep resistance for the sheath-core materials used in EX1-EX20 and CE 1.

Table 6: creep resistance and dimensional stability of sheath-core filament materials

Compounded sheath-core filament PSA Properties

Table 7 shows the test results of shear stress, 180 degree peel and optical haze for the sheath-core materials used in EX1-EX20 and CE 1. EX6 and EX7 were excluded due to non-ideal stability test results.

Table 7: compounded filament PSA Properties

N/A means "not applicable" because the sample was a hand-wound barrel, not a coextruded filament

NT means no test was performed

All cited references, patents, and patent applications in the above application for letters patent are incorporated by reference herein in their entirety in a consistent manner. In the event of inconsistencies or contradictions between the incorporated reference parts and the present application, the information in the preceding description shall prevail. The preceding description, given to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.

Claims

1. A sheath-core filament, comprising:

Wherein

R₁Is hydrogen or methyl; and is

R₂Is an alkyl, heteroalkyl, aryl, aralkyl or alkaryl group;

Wherein

R₁Is hydrogen or methyl; and is

Wherein

2. The sheath-core filament of claim 1, wherein the non-adherent sheath comprises a polymer selected from the group consisting of (meth) acrylic block copolymers, ethylene methyl copolymers, and combinations thereof.

3. The sheath-core filament of claim 1 or claim 2, wherein 1% to 10% of the longest cross-sectional distance of the sheath-core filament is sheath and 90% to 99% of the longest cross-sectional distance of the sheath-core filament is core.

4. The sheath-core filament according to any one of claims 1 to 3, wherein the curable (meth) acrylate copolymer has a weight average molecular weight in the range of 200kDa to 1500 kDa.

5. The sheath-core filament of any one of claims 1 to 4 wherein the curable adhesive composition further comprises an ionic crosslinking additive.

6. A cured adhesive composition comprising the sheath-core filament of any one of claims 1 to 5, the cured adhesive composition being a reaction product resulting from subjecting the sheath-core filament to ultraviolet or visible radiation after compounding the sheath-core filament through a heated extruder nozzle.

7. The cured adhesive composition of claim 6, wherein the cured adhesive composition exhibits a creep resistance of greater than 3MPa-s, greater than 5MPa-s, or greater than 8MPa-s when tested according to the creep resistance test method.

8. The cured adhesive composition of claim 6 or claim 7, wherein the cured adhesive composition is capable of being cured at room temperature at 323mm²A shear force of 1kg for at least 100 minutes, at least 1000 minutes, or at least 5000 minutes was maintained on the stainless steel panel.

9. The cured adhesive composition of any one of claims 6-8, wherein the cured adhesive composition exhibits a peel adhesion to stainless steel of at least 30N/cm when tested according to the 180 ° peel test method.

10. The cured adhesive composition of any one of claims 6 to 9, wherein the cured adhesive composition is formed after exposure to ultraviolet or visible radiation for less than 10 seconds, less than 5 seconds, or less than 2 seconds.

11. An article comprising a first substrate, a second substrate, and a layer of the cured adhesive composition of any one of claims 6 to 10, wherein the layer of the cured adhesive composition is positioned between the first substrate and the second substrate.

12. A method of making a sheath-core filament, the method comprising:

a) forming a core composition comprising the curable binder composition of claim 1;

13. The method of claim 12, wherein wrapping the skin composition around the core composition comprises co-extruding the core composition and the skin composition such that the skin composition surrounds the core composition.